The present invention relates to strong-acid cation exchange resins and to a process for producing such resins.
Strong-acid cation exchange resins and their use in the production of bisphenols are generally known in the art. U.S. Pat. No. 5,212,206 discloses a strong acid cation-exchange resin which is neutralized with a mercaptoamine in an anhydrous medium. U.S. Pat. No. 3,760,006 teaches that the modification of a strong-acid cation exchange resin in acid form by partial neutralization with a thiazolidine yields an improved catalyst for the preparation of bisphenol. U.S. Pat. No. 4,584,416 discloses partial neutralization of a sulfonated ion exchange resin by means of an N-alkylamino alkylmercaptan hydrochloride or hydrotosylate salt. U.S. Pat. No. 4,595,704 discloses that known methods for producing partially neutralized ion-exchange resins employ azirine compounds which are somewhat hazardous. The U.S. patent suggests the use of less costly and less hazardous N-(2-mercaptoalkyl)amides to prepare a strong-acid cation exchange resin which is partially neutralized with an aminoalkanethiol. U.S. Pat. No. 6,740,684 discloses a process wherein a strong-acid cation exchange resin in acid form is contacted with an alkyl carbamoyl alkyl thioester to produce a cation exchange resin wherein the acid groups are partially neutralized with a mercaptoalkylamine.
Bisphenols are prepared on very large scale, specifically bisphenol A is produced at an amount of more than a million metric tons/year. Therefore, there is a constant need to find new cation exchange resins which are useful for producing bisphenols of high selectivity. Accordingly, one object of the present invention is to provide a new cation exchange resin which is useful for producing bisphenols. A preferred object of the present invention is to provide a new cation exchange resin which is useful for producing bisphenols, particularly bisphenol A, with a selectivity that is at least as good or preferably even better than the selectivity that is achieved with the aid of known cation exchange resins.